BRYOPHYTES AND LICHENS OF THE GALAPAGOS ISLANDS
A joint exploration by the University of Colorado Museum (USA)
and the University of Utrecht (Netherlands), April-July 1976
Supported in part by grants from the National Geographic Society and
the Netherlands Foundation for the Advancement of Tropical Research (WOTRO)
INTRODUCTION
The main purpose of this study was to complete explorations begun in 1964, of the flora
of mosses, liverworts, and lichens of the various islands, as a basis for writing a defInitive
Flora of the Galapagos Ialands. This project was directed by Dr W A Weber (USA), whose
work has been mainly on the lichens and mosses. Participants in the expedition were Dr S Rob
Gradstein and Mr J H M Sipman (University of Utrecht), concentrating on liverworts and
mosses, and Miss Jeannine Lanier (University of Colorado) assistant to Dr Weber, and
concentrating on lichens.
Approximately 1,800 collections of bryophytes and lichens were made on the following islands:
Floreana, Isabela (Volcans Alcedo, Cerro Azul, and the coastal areas ofWolO, Pinta, Pinzon,
Rabida, Santa Cruz, San Cristobal and Santiago (James Bay). After completion of the identifcation
and labelling, sets of these collections will be deposited in the herbaria of the Charles Darwin
Research Station and the Catholic University in Quito, as well as the home institutions of the
researchers. Copies of the final publication, written in English with Spanish summary, will be
made available to the central offIce of National Park Galapagos and the Darwin Research
Station. Interim reports, including an introduction to the lichens of the Galapagos have been
prepared, and Spanish versions are being made available through the Darwin Station.
In the present report, some of the major features of bryophyte and lichen distribution, in
relation to habitat and altitudinal zonation, are pointed out. These data should be considered
preliminary since many species identifications require verifIcation. In fact, identification,
especially with the crustose lichens, is a very diffIcult task because the literature is so scattered
and type collections of many species are extremely meagre and scattered in many herbaria
over the world. Many of the common large genera have never been monographed or summarised
critically. Providing keys, descriptions and illustrations of Galapagos species, in conjunction
with distribution and habitat data, will help to fill a gap in the literature and will permit comparisons regarding the cryptogamic flora vis-a-vis the phanerogam flora as to island endemism,
the crucial biological problem in the Galapagos Islands.
NOTES ON DISTRIBUTION IN THE GALAPAGOS
BRYOPHYTES: Previous publications reported about 145 species of bryophytes: 80 liverworts
and 65 mosses. This number will rise to c. 200 species of bryophytes (110 liverworts, 90 mosses)
as a result of our collections. We were able to rediscover over 95 per cent of the species
previously reported, and about 30 liverworts and 25 mosses were found new to Galapagos.
Several liverwort species, belonging to the genera Plagiochila, Frullania and Colura, are new to
Science. Of mosses almost 90 per cent of the species are neotropical in distribution, including
some rare taxa from Central America or the Caribbean area (Gymnostomiella orcuttii,
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Erpodium domingensis, Crossomitrium orbiculatum, Porotrichum insu/arumJ. Of liverworts
about 75 per cent of the species are rather common neotropical elements whereas almost
15 per cent are pantropical or even sub cosmopolitan. Probably not more than 5 per cent of
the bryophytes are endemic to Galapagos. Of liverworts less than 10 species might be true
endemics (Metzgeria grandiflora, Notothylas galapagensis, Plagiochila spini[era, Plagiochila
sp. nov., Radula galapagona, Riccia howellii, Frullania and Colura spp. nov.) whereas among
the mosses there may be one or two. However, the continuing inadequacy of our knowledge
of mainland South America's cryptogamic flora leaves most of these somewhat suspect. Like
ferns, bryophytes are easily dispersed by means of wind-carried spores over long distances and
therefore endemic species are not likely to occur on Galapagos.
.
Nevertheless, it appears that the bryophyte flora of the various islands of Galapagos is far
from uniform. Some islands are very rich in species while on other islands bryophytes are
totally lacking. Both qualitatively and quantitatively we found considerable differences in
the assemblage of the bryophyte flora of each island. These differences may be due to the
age of the island or volcano, climate (especially precipitation), soil or rock composition,
vegetation, and the influence of man and his cattle. Most bryophytes favor moist habitats,
bryophytes achieving dominance over lichens where moisture dominates as liquid water and
lichens dominating in areas bathed by fog. In Galapagos bryophytes therefore are more
common in the highlands, and in fact almost two-thirds of the species occur only above 350
metres. South-exposed slopes (with high precipitation) are usually richer in bryophytes than
the dryer north-exposed slopes as, for instance, on Santa Cruz, San Cristobal, Pinta and Cerro
Azul (lsabela). The total number of the species of liverworts encountered on the principal
investigated islands is as follows (data on mosses not yet available):
Santa Cruz
San Cristobal
Cerro Azul
Pinta
Floreana
35 spp.
Alcedo (Isabela) 35 spp.
Pinzon
25 spp.
60 spp.
60 spp.
50 spp.
40 spp.
Since bryophytes are very poorly represented in the arid zone they are rare on dry islands such
as Espanola, Genovesa, Marchena (mosses occur here only around fumaroles), Rabida (a few
liverworts at the summit), Santa Fe and the volcanos Wolf and Darwin (lsabela). On the smaller
islets they are probably totally lacking. Santiago, Sierra Negra (Isabela) and Fernandina have
not been investigated. From our preliminary data we might suggest that the bryophyte flora
of Santiago is comparable to or slightly richer than that of Pinta, whereas the Sierra Negra
flora and that of Fernandina might in richness not exceed those of Floreana viz. Pinzon. The
richest bryophyte areas in Galapagos are the southern slopes of Santa Cruz, San Cristobal and
Cerro Azul on Isabela. These are probably the areas of Galapagos where the highest rainfalls
occur and the most reliable.
VEGETATION OR HABITATS WITH HIGHEST SPECIES DIVERSITY:
1. Scalesia pedunculata or Zanthoxylum woodlands, as on Santa Cruz (300-700 m) and
Pinta (350-600 m). In these moist, dense woodlands growth of epiphytic bryophytes (on
trees and shrubs) is luxuriant; festoons hang down from branches and twigs of the mosses
Meteoriopsis patula (200-600 m), Squamidium spp. (3 species, mainly above 500 m) and
liverworts belonging to the genus Frullania and genera of Lejeuneaceae. More than 50 per
cent of the liverworts ofGalapagos belong to these two groups. The festoon-forming bryophytes
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are the principal components of the nests of woodland birds. Many organisms, eg: snails, are
found inside the dense bryophyte mats, which contain large quantities of moisture. On Floreana
and San Cristobal this type of woodland has been (gradually) changed into monotonous
Psidium guaiava stands which are poorer in species.
2. Miconia-Cyathea shrub of Santa Cruz and San Cristobal. This type of vegetation is
probably best developed at present in the "encanadas" of southern San Cristobal (see below.).
The soil below Miconia and Cyathea is usually carpeted by a thick mat of liverworts. On
Santa Cruz, around Media Luna, Miconia stands are lower and disturbed by cattle; there the
ground cover is made up of mosses. Twigs of Miconia invariably have festoons of the liverwort
Ceratolejeunea cornuta which occurs exclusively in this vegetation type. The evergreen leaves
of Miconia are of interest because minute, rare liverworts and lichens grow on them.
3. The permanent streams of San Cristobal, between El Junco and Bahia de Agua Dulce.
The alluvial soils along the running water in the "encanadas" of southern San Cristobal are
carpeted by bryophytes, especially liverworts. About 10 new species for Galapagos, including
4 new genera, were found here. The flora in general of the permanent streams (including
waterfalls!) is unique for Galapagos and it is hoped it can be preserved for the future.
4. The "pampas" of Cerro Azul. These are the wettest and most extensive true pampa
(treeless) areas of Galapagos, extending from 300m to the top of the volcano. Their soils
provide the best habitats for thallose liverworts such as Marchantia, Riccia, Fossombronia and
Anthoceros, and small mosses, eg: Bryum spp. and Philonotis. They thrive on open, moist
soil trampled by cattle. The moss Enthostodon bonplandii, new to Galapagos, grows exclusively
here, and in great quantity! Of 23 species of thallose liverworts known to Galapagos, 7 occur
exclusively on the pampas of Cerro Azul, among them the Patagonian Sauteria berteroana
found only at altitudes of 130G-1400m !
On the SE slope of Cerro Azul, at an altitude of c. 800m, an area with two small adjacent
craters has the most luxuriant terricolous and saxicolous bryophyte vegetation seen anywhere
in Galapagos. Ferns are abundant here, too. Species belonging to the typical ltigh-Andean
paramo moss genera Breutelia and Thuidium are abundant as well as species of the liverwort
genera Herbertus and Bazzania. Ca. 5 bryophyte species are exclusively found in the paramolike area, for the "dry" Galapagos Islands an extraordinary kind of landscape. The SphagnumCyathea vegetation seen everywhere on the walls of the two craters resembles Color Plate 59
in Wiggins & Porters (1971), "Flora of the Galapagos Islands".
LICHENS: Previous publications (Weber 1966) reported about 76 species. Unfortunately, the
taxonomy of the lichens before 1950 was very primitive and a great many of these reports are
based on misidentifications. Nevertheless, approximately that number can be accepted under
their correct names, although a few reports based on the older expeditions evidently were
erroneously attributed to the Galapagos Islands. At the present time we have a total of 226
species fairly well identified and probably over one hundred unidentified, so that the total
oflichen species will approach 400. It will probably be a very long time before identifications
can be made on some of the larger, common crustose genera where one must really await careful
monograph treatment. It is best to refrain from making hasty identifications in these difficult
groups.
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Phytogeographically, the lichens may be sorted into several groups. Because of the facts stated
above, some of our feelings about phytogeography and endemism have to be tentative. However,
it is beginning to appear that there is a distinct endemic segment, that of the saxicolous lichens
inhabiting the rocks of the immediate ,coast or, if at higher elevations, still enjoying the
ecological conditions of the coastal area. It is obvious that high humidity is necessary for the
survival of this element, as can be seen on areas on the low islands where, back from the sea,
the horizontal faces of the rocks are too dry and hot to support lichens, while the same rocks
may support rich assemblages on their vertical faces where they receive greater protection
from the sun, and are occasionally bathed by moist air and fog. The coastal rocks of Galapagos,
wherever they have pronounced vertical aspects, are visible from great distances as being lichencoloured, the predominant colors being white, yellow and orange.
The coastal rock lichens tend to belong to genera and taxonomic groups closely related to the
coastal Chilean lichen flora. Several of these have been shown to be endemic to Galapagos
(Buellia gaZapagona, RocceZla galapagosense) and we found in 1976 one species, Lecidea
chilena, formerly believed to be endemic to Chile. We suspect that a high proportion of these
lichens will prove to be endemic.
The rock lichens of the interior tend to be more widely distributed lichens with geographical
affinities more with Central America and the Caribbean than with the South American mainland. The rock lichens of the moist highlands are relatively few in number and tend to be very
widely distributed highland species.
The corticolous lichens of the Galapagos appear to be, with very few exceptions, species at
least known elsewhere in the neotrophic~ or actually very common Neotropical species. A few
are highly disjunct, suggesting that collecting on the mainland is still too poor to give proper
indications of distribution. For example, a common lichen on Santa Cruz, Schistophoron
tenue, was previously known only from lowland open forests of West Africa! Many of the
smaller crustose lichens. growing on bark belong to groups which are very poorly understood
taxonomically.
The fruticose lichens occurring on the summit highlands in the fern-sedge zone tend to belong
to groups characteristic of the Andean and Central American highlands. Those few which have
been considered endemic are questionably so. Cladia aggregata is a very common highland
lichen throughout the southern Hemisphere. The highland lichen flora is not very rich since
it cannot eaSily compete with the rank growth of ferns, sedges, liverworts, and mosses. Crustose
species growing on rocks are limited to only it few species: TrapeZia coarctata, Diploschistes
scruposus, Leprocaulon microscopicum, etc.
While lichens are not particularly diversifed on the tronks of trees in the Scalesia forests, some
of the more interesting species occur there alone. Some of these species are extremely rare
and scattered; it is here that we encounter Erioderma, Pseudocyphellaria, Sticta, Leptogium the larger foliose lichens with the highest moisture requirements. A few of these, such as
Leptogium ssp. and Sticta weigelii find alternative substrates on the ground in the fern-sedge
zone, where they form a dense cover on the bare soil between vegetation patches. The complex
genus Parmelia, recently divided into a number of smaller genera, is ubiquitous on the islands,
several species occupying almost every lichen niche, whether rock, bark, or soil. Cladonia is
well represented and diversified particularly on the rocks and soil of the moister zones. Roccella
babingtonii is dominant and very conspicuous on the bare branches of trees in the Bursera
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forest and in historic times was an important export to the mainland since it was used to
produce purple dyes.
CONCLUDING REMARKS:
1. The present investigation has yielded total of c. 200 bryophytes and 400 lichen species
for Galapagos. Over 80 per cent of the bryophytes are rather commun nedtropical taxa, while
at most 5 per cent are endemics. The si:atistics for lichens are not reliable at the present time,
but the percentage of endemics will be higher because of a s!rong endemism of the coastal
rock species.
2. The islands with the highest species diversity are Santa Cruz, San Cristobal and Volcano
Cerro Azul on Isabela. Apparently bryophytes favor moist sites with high humidity rather
than liquid moisture. About two 'hirds of the bryophytes occur exclusively above 350m, while
lichens are more evenly distributed through the dry and moist zones. The richest habitats for
bryophytes on Galapagos are:
A
B.
C.
D.
Moist Scalesia pedunculata or Zanthoxylum woodlands, as on Santa Cruz and
Pinta.
Miconkl-Cyathea scrub (S. Cruz, S. Cristobal).
Permanent streams of San Cristobal.
Pampas on southern slopes of Cerro Azul.
3. Considerable differences are seen in the assemblag~s of bryophyte floras of the different
islands. The causes of these differences need further hwestigation. Thllre is very little difference
between islands as to lichen assemblages except that the a..:'titude of the islands determines
whether the more mesic element will be present.
4. Future protection of the permanent streams of San Cristobal should be considered, in
view of its unique bryophyte flora.
William A Weber
S R Gradstein
Jeannine Lanier
HJ M Sipman
26 September 1976
Warbler Finch
Certhidea olivacea
Drawing by Peter Scott.
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